Selective Chemical Fining of Small Bubbles in Glass

ABSTRACT

A method of fining glass is disclosed that includes flowing a molten glass bath through a fining chamber. The molten glass bath has an undercurrent that flows beneath a skimmer that is partially submerged in the molten glass bath. One or more fining agents are introduced into the undercurrent of the molten glass bath directly beneath the skimmer from a dissolvable fining material component. In this way, the fining agent(s) may selectively target the gas bubbles drawn under the skimmer within the undercurrent of the molten glass for removal. The method may be employed to fine molten gas produced in a submerged combustion melter. A fining vessel for fining molten glass is also disclosed.

The present disclosure is directed to glass fining and, morespecifically, to techniques for targeting and selectively exposing smallbubbles, which might otherwise be too small to quickly ascend to theglass surface, to a fining agent.

BACKGROUND

Glass is a rigid amorphous solid that has numerous applications.Soda-lime-silica glass, for example, is used extensively to manufactureflat glass articles including windows, hollow glass articles includingcontainers such as bottles and jars, and also tableware and otherspecialty articles. Soda-lime-silica glass comprises a disordered andspatially crosslinked ternary oxide network of SiO₂—Na₂O—CaO. The silicacomponent (SiO₂) is the largest oxide by weight and constitutes theprimary network forming material of soda-lime-silica glass. The Na₂Ocomponent functions as a fluxing agent that reduces the melting,softening, and glass transition temperatures of the glass, as comparedto pure silica glass, and the CaO component functions as a stabilizerthat improves certain physical and chemical properties of the glassincluding its hardness and chemical resistance. The inclusion of Na₂Oand CaO in the chemistry of soda-lime-silica glass renders thecommercial manufacture of glass articles more practical and less energyintensive than pure silica glass while still yielding acceptable glassproperties. Soda-lime-silica glass, in general and based on the totalweight of the glass, has a glass chemical composition that includes 60wt % to 80 wt % SiO₂, 8 wt % to 18 wt % Na₂O, and 5 wt % to 15 wt % CaO.

In addition to SiO₂, Na₂O, and CaO, the glass chemical composition ofsoda-lime-silica glass may include other oxide and non-oxide materialsthat act as network formers, network modifiers, colorants, decolorants,redox agents, or other agents that affect the properties of the finalglass. Some examples of these additional materials include aluminumoxide (Al₂O₃), magnesium oxide (MgO), potassium oxide (K₂O), carbon,sulfates, nitrates, fluorines, chlorines, and/or elemental or oxideforms of one or more of iron, arsenic, antimony, selenium, chromium,barium, manganese, cobalt, nickel, sulfur, vanadium, titanium, lead,copper, niobium, molybdenum, lithium, silver, strontium, cadmium,indium, tin, gold, cerium, praseodymium, neodymium, europium,gadolinium, erbium, and uranium. Aluminum oxide is one of the morecommonly included materials—typically present in an amount up to 2 wt %based on the total weight of the glass—because of its ability to improvethe chemical durability of the glass and to reduce the likelihood ofdevitrification. Regardless of what other oxide and/or non-oxidematerials are present in the soda-lime-glass besides SiO₂, Na₂O, andCaO, the sum total of those additional materials is preferably 10 wt %or less, or more narrowly 5 wt % or less, based on the total weight ofthe soda-lime-silica glass.

The manufacture of glass involves melting a vitrifiable feed material(sometimes referred to as a glass batch) in a furnace or melter within alarger volume of molten glass. The vitrifiable feed material may includevirgin raw materials, recycled glass (i.e., cullet), glass precursoroxides, etc., in proportions that result in glass having a certain glasscomposition upon melting and reacting of the feed material. When thevitrifiable feed material is melted into glass, gas bubbles of varioussizes are typically produced and become entrained within the glass. Theproduction of gas bubbles is especially pronounced if the vitrifiablefeed material is melted in a submerged combustion melter that includessubmerged burners positioned to fire their combustion products directlyinto the glass melt. The quantity of gas bubbles entrained within theglass may need to be reduced to satisfy commercial specifications for“bubble free” glass. The removal of gas bubbles—a process known as“fining”—may be warranted for various reasons including the visualappearance of the glass when cooled and formed into a finishedcommercial article such as a glass container, flat glass product, ortableware. Glass fining has traditionally been accomplished by heatingthe glass to achieve a glass viscosity more conducive to bubbleascension and/or by adding a fining agent into the glass.

A fining agent is chemical compound that reacts within the glass atelevated temperatures to release fining gases such as O₂, SO₂, and/orpossibly others into the glass. The fining gases help eradicate smallergas bubbles that result from melting of the vitrifiable feed materialother than those attributed to the fining agent (“native bubbles”). Thefining gases, more specifically, form new gas bubbles (“fining bubbles”)and/or dissolve into the glass melt. The fining bubbles rapidly ascendto the surface of the glass—where they ultimately exit the glass meltand burst—and during their ascension may sweep up or absorb the smallernative gas bubbles along the way. The fining gases that dissolve intothe glass melt may diffuse into the smaller native bubbles to increasethe size and the buoyancy rise rate of those bubbles. The fining gasesmay also change the redox state [(Fe′/(Fe′+Fe′) in which Fe′ isexpressed as FeO and Fe′ is expressed as Fe₂O₃] of the glass and causesome of the smaller native bubbles to disappear as the gas(es) in thosebubbles dissolves into the glass melt. Any one or a combination of thesemechanisms may be attributed to the fining agent.

A fining agent has traditionally been added to the vitrifiable feedmaterial or metered separately into the glass. Whether the fining agentis included in the vitrifiable feed material or added separately, theresultant fining gases interact indiscriminately with gas bubbles of allsizes within the glass. Such broad exposure of the fining gases to allgas bubbles is somewhat inefficient since the larger native bubbles willquickly ascend through the glass and burst on their own regardless ofwhether a fining agent is added to the glass. Additionally, if thefining agent is introduced separately from the vitrifiable feedmaterial, mechanical stirring may be used to uniformly mix the finingagent throughout the glass. But stirring the glass breaks larger nativebubbles into smaller gas bubbles and counteracts the fining process bydrawing bubbles (both large and small) back down into the glass awayfrom the surface of the glass. As such, to clear the glass of bubbles,the amount of the fining agent added to the glass is usually based onthe total amount of native gas bubbles that may be contained in theglass even though the smaller native bubbles dictate how much time isrequired to fine the glass since those bubbles ascend through the glassat the slowest pace or do not ascend at all.

The current practices of unselectively introducing a fining agent intothe glass requires the consumption of an excess amount of the finingagent. This can increase the cost of materials as well as the operatingcosts associated with the fining process. Moreover, the fining processis not as optimized as it could be due to the oversupply of the finingagent and the corresponding fining activity that must be supported,which results in additional fining time beyond what is theoreticallyrequired to remove only the smaller native bubbles. The presentdisclosure addresses these shortcomings of current fining procedures byselectively exposing the smaller native bubbles in the glass to one ormore fining agents. The targeted exposure of smaller native bubbles tothe fining agent(s) may reduce the need to add excessive amounts of thefining agent to the glass, thus saving material and energy costs, andmay also speed the overall fining process since the fining gasesintroduced into the glass can be minimized while still targeting andremoving the smaller native bubbles. The fining agent(s) do notnecessarily have to be exposed to the larger native bubbles since doingso is unlikely to have a noticeable impact on the amount of time ittakes to fine the glass.

SUMMARY OF THE DISCLOSURE

The present disclosure is directed to an apparatus and method for finingglass. The apparatus is a fining vessel that receives an input moltenglass. The input molten glass has a first density and a firstconcentration of entrained gas bubbles. The fining vessel may be astand-alone tank that receives the input molten glass from a separatemelter, such as a submerged combustion melter, or it may be part of alarger Siemens-style furnace that receives the input molten glass froman upstream melting chamber. The input molten glass is combined with andsubsumed by a molten glass bath contained within a fining chamberdefined by a housing of the fining vessel. The molten glass bath flowsthrough the fining chamber along a flow direction from an inlet to anoutlet of the fining vessel. Output molten glass is discharged from thefining vessel after flowing through the fining chamber. The outputmolten glass has a second density that is greater than the first densityand a second concentration of entrained gas bubbles that is less thanthe first concentration of entrained gas bubbles. To facilitate finingof the glass, a skimmer is partially submerged in the molten glass bath.The skimmer defines a submerged passageway together with correspondingportions of the housing of the fining vessel. An undercurrent of themolten glass bath flows through the submerged passageway and is exposedto one or more fining agents beneath the skimmer to better targetsmaller gas bubbles for removal.

The present disclosure embodies a number of aspects that can beimplemented separately from or in combination with each other. Accordingto one embodiment of the present disclosure, a method of fining glassincludes several steps. One step of the method involves supplying inputmolten glass into a fining chamber of a fining vessel. The input moltenglass combines with a molten glass bath contained within the finingchamber and introduces entrained gas bubbles into the molten glass bath.The input molten glass has a density and a concentration of gas bubbles.Another step of the method involves flowing the molten glass baththrough the fining chamber in a flow direction. The molten glass bathhas an undercurrent that flows beneath a skimmer, which is partiallysubmerged in the molten glass bath, and through a submerged passagewaydefined in part by the skimmer. Still another step of the methodinvolves introducing one or more fining agents into the undercurrent ofthe molten glass bath directly beneath the skimmer from a dissolvablefining material component.

According to another aspect of the present disclosure, a method ofproducing and fining glass includes several steps. One step of themethod involves discharging combustion products from one or moresubmerged burners directly into a glass melt contained within aninterior reaction chamber of a submerged combustion melter. Thecombustion products discharged from the one or more submerged burnersagitate the glass melt. Another step of the method involves dischargingfoamy molten glass obtained from the glass melt out of the submergedcombustion melter. Still another step of the method involves supplyingthe foamy molten glass into a fining chamber of a fining vessel as inputmolten glass. The input molten glass combines with a molten glass bathcontained within the fining chamber and introduces entrained gas bubblesinto the molten glass bath. The input molten glass has a density andcomprises up to 60 vol % bubbles. Yet another step of the methodinvolves flowing the molten glass bath through the fining chamber in aflow direction. The molten glass bath has an undercurrent that flowsbeneath a skimmer, which is partially submerged in the molten glassbath, and through a submerged passageway defined in part by the skimmer.Another step of the method involves introducing one or more finingagents into the undercurrent of the molten glass bath directly beneaththe skimmer from a dissolvable fining material component. And anotherstep of the method involves discharging output molten glass from thefining vessel. The output molten glass has a density that is greaterthan the density of the input molten glass and further comprises lessthan 1 vol % bubbles.

According to yet another aspect of the present disclosure, a finingvessel for fining glass includes a housing that defines a finingchamber. The housing has a roof, a floor, and an upstanding wall thatconnects the roof and the floor, and further defines an inlet to thefining chamber and an outlet from the fining chamber. The fining vesselalso includes a skimmer that extends downwards from the roof of thehousing towards the floor of the housing and further extends across thefining chamber between opposed lateral sidewalls of the upstanding wall.The skimmer has a distal free end that together with correspondingportions of the floor and the upstanding wall defines a submergedpassageway. Additionally, a dissolvable fining material component isdisposed directly beneath the skimmer. The dissolvable fining materialcomponent comprises a mixture of a glass compatible base material andone or more fining agents.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objects, features, advantages,and aspects thereof, will be best understood from the followingdescription, the appended claims, and the accompanying drawings, inwhich:

FIG. 1 is an elevated cross-sectional representation of a submergedcombustion melter and a fining vessel that receives molten glassproduced by the submerged combustion melter according to one embodimentof the present disclosure;

FIG. 2 is a cross-sectional plan view of the floor of the submergedcombustion melter illustrated in FIG. 1 and taken along section line2-2;

FIG. 3 is an elevated cross-sectional illustration of the fining vesseldepicted in FIG. 1 according to one embodiment of the presentdisclosure;

FIG. 4 is a cross-sectional plan view of the fining vessel depicted inFIG. 3 and taken along section line 4-4;

FIG. 5 is a magnified elevated cross-sectional view of a portion of thefining vessel illustrated in FIG. 3 including a skimmer positionedwithin the fining vessel according to one embodiment of the presentdisclosure;

FIG. 6 is cross-sectional view of the fining vessel taken along sectionlines 6-6 in FIG. 5;

FIG. 7 is a cross-sectional view of the fining vessel taken from thesame perspective as that of FIG. 6 showing the skimmer according toanother embodiment of the present disclosure;

FIG. 8 is a cross-sectional view of the fining vessel taken from thesame perspective as that of FIG. 6 showing the skimmer according to yetanother embodiment of the present disclosure;

FIG. 9 is a magnified elevated cross-sectional view of a skimmerpositioned within the fining vessel illustrated in FIG. 3 according tostill another embodiment of the present disclosure;

FIG. 10 is a cross-sectional view of the fining vessel taken alongsection lines 10-10 in FIG. 9;

FIG. 11 is a magnified view of the skimmer illustrated in FIG. 3; and

FIG. 12 is a flow diagram of a process for forming glass containers fromthe output molten glass discharged from the fining vessel according toone embodiment of the present disclosure.

DETAILED DESCRIPTION

The disclosed apparatus and fining method are preferably used to finemolten glass produced by melting a vitrifiable feed material viasubmerged combustion melting. As will be described in further detailbelow, submerged combustion melting involves injecting a combustible gasmixture that comprises fuel and an oxidant directly into a glass meltcontained in a submerged combustion melter though submerged burners. Thecombustible gas mixture autoignites and the resultant combustionproducts cause vigorous stirring and turbulence as they are dischargedthrough the glass melt. The intense shearing forces experienced betweenthe combustion products and the glass melt cause rapid heat transfer andparticle dissolution throughout the glass melt. While submergedcombustion technology can melt and integrate a vitrifiable feed materialinto the glass melt relatively quickly, thus resulting in relatively lowglass residence times, the glass melt tends to be foamy and have arelatively low density despite being chemically homogenized whendischarged from the melter. Fining foamy molten glass discharged fromthe glass melt in accordance with the present disclosure can render thefining process more efficient. Of course, molten glass produced in othertypes of melting apparatuses, including a melting chamber of aconventional Siemens-style furnace, may also be fined in the same way.

Referring now to FIGS. 1-5, a glass fining vessel 10 is depictedaccording to one embodiment of the present disclosure. The glass finingvessel 10 receives an input molten glass 12 that originates from withina submerged combustion melter 14 and discharges output molten glass 16for additional processing into a finished article. The glass finingvessel 10 has a housing 18 that defines a fining chamber 20 in which amolten glass bath 22 is contained. The housing 18 further defines aninlet 24 through which the input molten glass 12 is received and anoutlet 26 through which the output molten glass 16 is discharged. Theinput molten glass 12 combines with and is subsumed by the molten glassbath 22, and the output molten glass 16 is drawn from the molten glassbath 22 at a location downstream from the inlet 24. As such, the moltenglass bath 22 flows through the fining chamber 20 in a flow direction Ffrom the inlet 24 to the outlet 26 of the glass fining vessel 10 whilebeing fined along the way as described in more detail below.

The housing 18 of the glass fining vessel 10 includes a roof 28, a floor30, and an upstanding wall 32 that connects the roof 28 and the floor30. The upstanding wall 32 typically includes an inlet or front end wall32 a, an outlet or back end wall 32 b, and two opposed lateral sidewalls32 c, 32 d that join the inlet end and outlet end walls 32 a, 32 b. Thehousing 18 of the fining vessel 10 is constructed from a one or morerefractory materials. Refractory materials are a class of inorganic,non-metallic materials that can withstand high-temperatures whileremaining generally resistant to thermal stress and corrosion. In oneparticular embodiment, the floor 30 and the glass-contacting portions ofthe upstanding wall 32 may be formed from fused cast AZS(alumina-zirconia-silicate), bond AZS, castable AZS, high alumina,alumina-chrome, or alumina-silica type refractories. Insulating bricksand ceramic fire boards may be disposed behind these portions of thehousing 18. As for the roof 28 and the superstructure (i.e., thenon-glass contacting portion of the upstanding wall 32), those portionsof the housing 18 may be formed from an alumina-silica refractory suchas mullite.

The inlet 24 to the fining vessel 10 may be defined in the roof 28 ofthe housing 18 proximate the inlet end wall 32 a, as shown, although itmay also be defined in the inlet end wall 32 a either above or below asurface 34 of the molten glass bath 22 or in one or both of the lateralsidewalls 32 c, 32 d either above or below the surface 34 of the moltenglass bath 22. The inlet 24 provides an entrance to the fining chamber20 for the introduction of the input molten glass 12 at a feed rate RF.The inlet 24 may be fluidly coupled to the submerged combustion melter14 or an intermediate holding tank (not shown) located between thesubmerged combustion melter 14 and the fining vessel 10 by a containedconduit or, in another implementation, such as the one illustrated here,the inlet 24 may be positioned in flow communication with the inputmolten glass 12 so that the input molten glass 12 can be poured into thefining chamber 20 while being exposed to the ambient environment. Anexample of an intermediate holding tank that may be fluidly positionedbetween the submerged combustion melter 14 and the fining vessel 10 isthe stilling vessel that is disclosed in a patent application titledSTILLING VESSEL FOR SUBMERGED COMBUSTION MELTER and having Docket No.19522, which is assigned to the assignee of the present invention and isincorporated herein by reference in its entirety.

The outlet 26 of the fining vessel 10 may be defined in the outlet endwall 32 b either adjacent to the floor 30 (as shown) or above the floor30 yet beneath the surface 34 of the molten glass bath 22. The outlet 26may also be defined in the floor 30 or in one or both of the lateralsidewalls 32 c, 32 d beneath the surface 34 of the molten glass bath 22and proximate the outlet end wall 32 b. The outlet 26 provides an exitfrom the fining chamber 20 for the discharge of the output molten glass16 at a discharge or pull rate R_(D). In the context of commercial glasscontainer manufacturing, the outlet 26 of the fining vessel 10 mayfluidly communicate with a spout chamber 36 of a spout 38 appended tothe outlet end wall 32 b. The spout 38 includes a spout bowl 40, whichdefines the spout chamber 36 along with an orifice plate 42, and furtherincludes at least one reciprocal plunger 44 that reciprocates to controlthe flow of accumulated output molten glass 46 held within the spoutchamber 36 through an aligned orifice 48 in the orifice plate 42 tofashion streams or runners of glass. These streams or runners of glassmay be sheared into glass gobs of a predetermined weight that can beindividually formed into glass containers upon delivery to a glasscontainer forming machine.

The fining vessel 10 includes a skimmer 50 positioned between the inlet24 and the outlet 26. As shown best in FIGS. 5 and 11, the skimmer 50extends downwardly from the roof 28 of the housing 18 and is partiallysubmerged in the molten glass bath 22. At least a submerged portion 52of the skimmer 50 extends across the fining chamber 20 between thelateral sidewalls 32 c, 32 d of the housing 18 and has an upstream face54, an opposite downstream face 56, and a distal free end 58 connectingthe upstream and downstream faces 54, 56. The distal free end 58 of theskimmer 50 defines a submerged passageway 60 along with correspondingportions of the floor 30 and the sidewalls 32 c, 32 d. The establishmentof the submerged passageway 60 causes an undercurrent 62 of the moltenglass bath 22 to flow beneath the skimmer 50 and through the submergedpassageway 60 as the glass bath 22 as a whole flows along the flowdirection F towards the outlet 26 of the fining vessel 10. The skimmer50 has a centerplane 64 that is parallel to a vertical reference plane66 (FIG. 11), which is perpendicular to the horizontal or gravity level,or angled at no more than 5° from the vertical reference plane 66 ineither direction.

At least one fining agent is introduced into the molten glass bath 22directly beneath the skimmer 50 in direct exposure to the undercurrent62 of the molten glass bath 22 from a dissolvable fining materialcomponent 68 that includes one or more fining agents. The term “directlybeneath the skimmer” as used herein refers to a zone 70 (FIG. 11) of thefining chamber 20 defined by sectioning the skimmer 50 where itsthickness S_(T) as measured between the upstream face 54 and thedownstream face 56 is greatest, and then extending first and secondplanes 70 a, 70 b from the upstream and downstream faces 54, 56 of theskimmer 50 where sectioned, respectively, parallel with the centerplane64 of the skimmer 50 such that the planes 70 a, 70 b intersect the floor30 and the upstanding wall 32 of the housing 18. The volume between theskimmer 50, the floor 30, the sidewalls 32 c, 32 d, and the extendedplanes 70 a, 70 b is the zone 70 that is considered to be directlybeneath the skimmer 50. By introducing at least one fining agent intothis zone 70, smaller gas bubbles can more easily be targeted forremoval.

The dissolvable fining material component 68 comprises a mixture of aglass compatible base material and one or more fining agents. Themixture may be physically compacted or bound together by a binder. Theglass compatible base material is any material that contributes onlycompounds into the glass that are already part of the glass chemicalcomposition. For instance, if the molten glass bath 22 is composed ofsoda-lime-silica glass, the glass compatible base material is formulatedto introduce one or more of Si₂O, Na₂O, or CaO, and/or any othercomponent of soda-lime-silica glass, into the molten glass bath 22. Tothat end, the glass compatible base material may be soda-lime-silicaglass, the vitrifiable feed material that is being melted in theupstream submerged combustion melter 14, pulverized soda-lime-silicacullet, a precursor oxide of soda-lime-silica glass such as SiO₂—Na₂O,Na₂O—CaO, or sodium silicate, or combinations thereof. The one or morefining agents may be any compound or a combination of compounds thatrelease fining gases into the molten glass bath 22. In particular, thefining agent(s) may include a sulfate such as sodium sulfate (saltcake), which decomposes to release O₂ and SO₂ as the fining gases. Otherfining agents that may be employed include Cr₂O₃, WO₃, reactive carbon,aluminum, a carbonate, silicon carbide (SiC), or an oxidized metalpowder.

The dissolvable fining material component 68 may be disposed directlybeneath the skimmer 50 in several different ways. In one implementation,as shown best in FIG. 11, the dissolvable fining material component 68is a solid plate 72 supported within the skimmer 50. The plate 72 has anexposed portion 74 that protrudes a distance PD beyond the distal freeend 58 of the skimmer 50 that is less than a distance T_(D) between thefree end 58 of the skimmer 50 and the floor 30 of the housing 18. Inthis construction, the skimmer 50 has a main body 76 that defines aninternal cavity 78. The internal cavity 78 has a width C_(W) (FIG. 4)that extends along a width S_(W) of the skimmer 50—the skimmer widthS_(W) being the size dimension of the skimmer 50 in a directionextending between the lateral sidewalls 32 c, 32 d—and a thickness C_(T)(FIG. 11) that extends along the thickness S_(T) of the skimmer 50. Thewidth and thickness C_(W), C_(T) of the internal cavity 78 are both lessthan the width and thickness S_(W), S_(T) of the skimmer 50. Theinternal cavity 78 also has a height C_(H) (FIG. 11) that extends alonga height S_(H) of the skimmer 50—the skimmer height S_(H) being the sizedimension of the skimmer 50 in a direction extending between the roof 28and the floor 30—while traversing the skimmer 50 such that the cavity 78is open at the distal free end 58 and an opposed upper end 80 of theskimmer 50. The opposed upper end 80 of the skimmer 50 is preferablyheld outside of the fining chamber 20 by the housing 18 of the finingvessel 10.

The dissolvable fining material plate 72 may be inserted into theinternal cavity 78 through the opposed upper end 80 of the skimmer 50and, additionally, is moveable relative to the main body 76 along theheight S_(H) of the skimmer 50. The moveable nature of the dissolvablefining material plate 72 permits the plate 72 to be slid downwardlythrough the skimmer 50 and past the distal free end 58 of the skimmer 50towards the floor 30 of the housing 18. The plate 72 may be slid at aconstant velocity or intermittently as needed. In that regard, as theexposed portion 74 of the plate 72 disintegrates over time due toconstant exposure to the undercurrent 62 of the molten glass bath 22passing through the submerged passageway 60, the plate 72 may beadvanced to maintain the exposed portion 74 at the desired distance PDbeyond the distal free end 58 of the skimmer 50.

To help ensure that the portion of the plate 72 within the main body 74is preserved, the main body 76 may be constructed from a refractorymaterial, such as the refractories disclosed above for theglass-contacting portions of the upstanding wall 32, and is preferablyliquid cooled. The main body 76 may be liquid cooled by a distributionof cooling tubes 82 encased within the main body 76 that fluidlycommunicate with an inlet cooling tube 84 and an outlet cooling tube 86.A cooling fluid such as water may be circulated into the inlet coolingtube 84, through the distribution of cooling tubes 82, and out of theoutlet cooling tube 86 to maintain the main body 76, especially the partwithin the submerged portion 52 of the skimmer 50, at a temperaturebelow the temperature of the molten glass bath 22. In many instances, atemperature differential between a temperature of the cooling fluidentering the main body 76 of the skimmer 50 at the inlet cooling tube 84and a temperature of the cooling fluid exiting the main body 76 of theskimmer 50 at the outlet cooling tube is maintained at less than 20° C.,or more narrowly between 5° C. and 15° C. This condition creates a thinlayer of high viscosity glass melt immediately adjacent to the submergedportion 52 of the skimmer 50, which, in turn, protects the skimmer 50against thermal and corrosive damage and extends the operationallifetime of the skimmer 50.

The skimmer 50 may separate gas bubbles 88 introduced into the moltenglass bath 22 by the input molten glass 12 according to the size of thegas bubbles 88. As discussed above, the input molten glass 12 containsbubbles of various sizes as a result of melting the vitrifiable feedmaterial in the submerged combustion melter 14. The input molten glass12 has a first density and first concentration of entrained gas bubbles.Here, as a result of submerged combustion melting, the input moltenglass 12 typically has a density between 0.75 gm/cm³ and 1.5 gm/cm³, ormore narrowly between 0.99 gm/cm³ and 1.3 gm/cm³, and concentration ofentrained gas bubbles ranging from 30 vol % to 60 vol % forsoda-lime-silica glass. The gas bubbles carried within the input moltenglass 12 and added to the molten glass bath 22 have a diameter thattypically ranges from 0.10 mm to 0.9 mm and, more narrowly, from 0.25 mmto 0.8 mm. Compared to gas bubbles having a diameter of greater than 0.7mm, gas bubbles having a diameter of 0.7 mm or less are more likely toremain suspended in the deeper regions of the molten glass bath 22 asthe molten glass bath 22 flows along the flow direction F. The densityand bubble concentration values stated above may be different. Forexample, if the input molten glass 12 is obtained from a Siemens-stylemelting furnace, the density and bubble concentration values wouldlikely be greater than, and less than, the above-stated ranges,respectively, for soda-lime-silica glass.

The skimmer 50 can be sized and positioned to achieve the desiredseparation of the gas bubbles 88. Each of the following three designcharacteristics of the skimmer 50 effects the size of the bubbles thatpass beneath the skimmer 50 and through the submerged passageway 60: (1)a distance S_(D) between the centerplane 64 of the skimmer 50 at theaxial free end 58 and the inlet end wall 32 a along the flow directionF; (2) the distance T_(D) between the free end 58 of the skimmer 50 andthe floor 30 of the housing 18; and (3) the discharge rate R_(D) of theoutput molten glass 16 through the outlet 26 of the fining vessel 10. Byincreasing the distance S_(D) between the skimmer 50 and the inlet endwall 32 a (characteristic 1 above), the bubbles 88 have more time toascend to the surface 34 of the molten glass batch 22 and burst beforereaching the upstream face 54 of the skimmer 50. Likewise, decreasingthe distance S_(D) between the skimmer 50 and the inlet end wall 32 aprovides the bubbles 88 with less time to ascend to the surface 34 ofthe molten glass bath 22 and burst. Accordingly, the size of the gasbubbles 88 that are drawn under the skimmer 50 within the undercurrent62 tends to decrease as the distance S_(D) between the skimmer 50 andthe inlet end wall 32 a increases.

Additionally, the size of the gas bubbles 88 that are drawn under theskimmer 50 within the undercurrent 62 tends to decrease as the distanceT_(D) between the free end 58 of the skimmer 50 and the floor 30 of thehousing 18 (characteristic 2 above) decreases, and vice versa. Indeed,as the distance T_(D) between the free end 58 of the skimmer 50 and thefloor 30 decreases, the skimmer 50 is submerged deeper into the moltenglass bath 22 and the size of the gas bubbles 88 that are drawn underthe skimmer 50 within the undercurrent 62 also decreases. Conversely, asthe distance T_(D) between the free end 58 of the skimmer 50 and thefloor 30 increases, the skimmer 50 is submerged shallower into themolten glass bath 22, and the size of the gas bubbles 88 being drawnunder the skimmer 50 within the undercurrent 62 increases since moltenglass closer to the surface 34 of the molten glass bath 22 can now flowbeneath the skimmer 50. Lastly, a higher discharge rate R_(D) of theoutput molten glass 16 (characteristic 3 above) reduces the residencetime of the molten glass bath 22 and tends to increase the size of thegas bubbles 88 that are drawn under the skimmer 50 within theundercurrent 62, while a lower discharge rate R_(D) of the output moltenglass 16 has the opposite effect.

By balancing the three design characteristics set forth above, theskimmer 50 may be sized and positioned so that the gas bubbles 88 thatpass beneath the skimmer 50 within the undercurrent contain at least 95%of smaller gas bubbles that have diameters of less than 0.7 mm or, morepreferably, less than 0.5 mm. The larger gas bubbles having diameters of0.7 mm or greater ascend too quickly and eventually rise to the surface34 of the molten glass bath 22 upstream of the skimmer 50 and burst. Inone implementation of the skimmer 50, in which the glass discharge rate(characteristic 3) is 100 tons per day, the first and second designcharacteristics set forth above may lie within the ranges detailed belowin Table 1 to achieve at least 95% of smaller gas bubbles within theundercurrent 62, although other combinations of characteristics 1-3 arecertainly possible.

TABLE 1 Skimmer Parameters (100 tpd glass discharge rate) ParameterRange S_(D) 180 Feet to 250 Feet  T_(D) 3 Inches to 10 InchesUsing the skimmer 50 to separate the gas bubbles 88 so that a contingentof smaller gas bubbles primarily passes beneath the skimmer 50 isadvantageous in one respect; that is, the separation ensures that thesmaller gas bubbles carried by the undercurrent 62 through the submergedpassageway 60 are selectively exposed to the dissolvable fining materialcomponent 68 and the fining gases produced from the fining agent(s)released from the component 68 into the molten glass bath 22.

The housing 18 of the fining vessel 10 may also support one or morenon-submerged burners 90 to heat the molten glass bath 22 and curtail anundesired increase in viscosity. Each of the non-submerged burners 90combusts a mixture of a fuel and an oxidant. The non-submerged burners90 may include one or more sidewall burners 90 a mounted in one or bothof the lateral sidewalls 32 c, 32 d of the housing 18, one or more roofburners 90 b mounted in the roof 28 of the housing 18, or both types ofburners 90 a, 90 b. For example, as shown in FIG. 5, a plurality ofsidewall burners 90 a may be mounted in one or both of the sidewalls 32c, 32 d in spaced relation along the flow direction F between the inlet24 and the outlet 26 of the fining vessel 10. Each of the plurality ofsidewall burners 90 a may be fixedly or pivotably mounted within aburner block. The combustion products 92 a emitted from the burners 90 amay be aimed into an open atmosphere 94 above the surface 34 of themolten glass bath 22 or, alternatively, may be aimed toward the moltenglass bath 22 so that the combustion products 92 a directly impinge thesurface 34 of the molten glass bath 22. The sidewall burners 90 a may bepencil burners or some other suitable burner construction.

In addition to or in lieu of the sidewall burner(s) 90 a, a plurality ofroof burners 90 b may be mounted in the roof 28 in spaced relation alongthe flow direction between the inlet 24 and the outlet 26 of the housing18. In some instances, and depending on the burner design, multiple rowsof roof burners 90 b may be spaced along the flow direction F of themolten glass bath 22, with each row of burners 90 b including two ormore burners 90 b aligned perpendicular to the flow direction F. Each ofthe roof burners 90 b may be a flat flame burner that supplieslow-profile combustion products 92 b and heat into the open atmosphere94 above the surface 34 of the molten glass, or, in an alternateimplementation, and as shown here, each burner 90 b may be a burner thatis fixedly or pivotably mounted within a burner block and aimed todirect its combustion products 92 b into direct impingement with the topsurface 34 of the molten glass bath 22. If a roof burner 90 b of thelatter impingement variety is employed, the burner is preferably mountedin the roof 28 of the housing 18 upstream of the skimmer 50 to suppressfoam build-up.

The non-submerged burner(s) 90 may be configured so that theircombustion products 92 impact the surface 34 of the molten glass bath 22to aid in the fining of particularly foamy molten glass such as, forexample, the glass produced in a submerged combustion melter. Foamyglass with a relatively high amount of bubbles can develop a layer offoam that accumulates on top of the molten glass bath 22. A layer offoam of this nature can block radiant heat flow and, as a result,insulate the underlying glass from any heat added to the open atmosphere94 by non-submerged burners 90 that emit non-impinging combustionproducts. One way to overcome the challenges posed by foam is to breakup or destroy the foam. Direct impingement between the combustionproducts 92 and the top surface 34 of the molten glass bath 22 candestroy and reduce the volume of any foam layer that may develop on topof the molten glass bath 22, which, in turn, can help improve heattransfer efficiency into the molten glass bath 22.

The operation of the fining vessel 10 will now be described in thecontext of fining glass produced in the upstream submerged combustionmelter 14. In general, and referring now to FIG. 1, the submergedcombustion melter (SC melter) 14 is fed with a vitrifiable feed material96 that exhibits a glass-forming formulation. The vitrifiable feedmaterial 96 is melt-reacted inside the SC melter 14 within an agitatedglass melt 98 to produce molten glass. Foamy molten glass 100 isdischarged from the SC melter 14 out of the glass melt 98. The foamymolten glass 100 is supplied to the fining vessel 10 as the input moltenglass 12. The input molten glass 12 combines with and is subsumed by themolten glass bath 22 contained in the fining chamber 20 of the finingvessel 10. The molten glass bath 22 flows along the flow direction Ffrom the inlet 24 of the fining vessel 10 to the outlet 26. As a resultof this flow, the undercurrent 62 of the molten glass bath 22 that flowsbeneath the skimmer 50 is directly exposed to the dissolvable finingmaterial component 68 and the fining agent(s) released from thecomponent 68. The introduction of fining agents into the molten glassbath 22 directly beneath the skimmer 50 can selectively target smaller,more-difficult-to-remove gas bubbles, especially if the skimmer 50 isused to separate the gas bubbles 88 introduced into the molten glassbath 22 from the input molten glass 12 based on bubble size.

The SC melter 14 includes a housing 102 that defines an interiorreaction chamber 104. The housing has a roof 106, a floor 108, and asurrounding upstanding wall 110 that connects the roof 106 and the floor108. The surrounding upstanding wall 110 further includes a front endwall 110 a, a back end wall 110 b that opposes and is spaced apart fromthe front end wall 110 a, and two opposed lateral sidewalls 110 c, 110 dthat connect the front end wall 110 a and the back end wall 110 b. Theinterior reaction chamber 104 of the SC melter 14 holds the glass melt98 when the melter 14 is operational. At least the floor 108 and thesurrounding upstanding wall 110 of the housing 102, as well as the roof106 if desired, may be constructed from one or more fluid-cooled panelsthrough which a coolant, such as water, may be circulated. Thefluid-cooled panels include a glass-side refractory material layer 112that may be covered by a layer of frozen glass 114 that forms in-situbetween an outer skin of the glass melt 98 and the refractory materiallayer 112. The glass-side refractory material layer 112 may beconstructed from any of the refractories disclosed above for theglass-contacting portions of the upstanding wall 32 of the housing 18 ofthe fining vessel 10.

The housing 102 of the SC melter 14 defines a feed material inlet 116, amolten glass outlet 118, and an exhaust vent 120. As shown in FIG. 1,the feed material inlet 116 may be defined in the roof 106 of thehousing 102 adjacent to or a distance from the front end wall 110 a, andthe molten glass outlet 118 may be defined in the back end wall 110 b ofthe housing 102 adjacent to or a distance above the floor 108, althoughother locations for the feed material inlet 116 and the molten glassoutlet 118 are certainly possible. The feed material inlet 116 providesan entrance to the interior reaction chamber 104 for the delivery of thevitrifiable feed material 96 by way of a batch feeder 122. The batchfeeder 122 is configured to introduce a metered amount of thevitrifiable feed material 96 into the interior reaction chamber 104 andmay be coupled to the housing 102. The molten glass outlet 118 outletprovides an exit from the interior reaction chamber 104 for thedischarge of the foamy molten glass 100 out of the SC melter 14. Theexhaust vent 120 is preferably defined in the roof 106 of the housing102 between the front end wall 110 a and the back end wall 110 b and isconfigured to remove gaseous compounds from the interior reactionchamber 104. And, to help prevent the potential loss of some of thevitrifiable feed material 96 through the exhaust vent 120, a partitionwall 124 that depends from the roof 106 of the housing 102 and ispartially submerged into the glass melt 98 may be positioned between thefeed material inlet 116 and the exhaust vent 120.

The SC melter 14 includes one or more submerged burners 126. Each of theone or more submerged burners 126 is mounted in a port 128 defined inthe floor 108 (as shown) and/or the surrounding upstanding wall 110 at aportion of the wall 110 that is immersed by the glass melt 98. Each ofthe submerged burner(s) 126 forcibly injects a combustible gas mixture Ginto the glass melt 98 through an output nozzle 130. The combustible gasmixture G comprises fuel and an oxidant. The fuel supplied to thesubmerged burner(s) 126 is preferably methane or propane, and theoxidant may be pure oxygen or include a high-percentage (>80 vol %) ofoxygen, in which case the burner(s) 126 are oxy-fuel burners, or it maybe air or any oxygen-enriched gas. Upon being injected into the glassmelt 98, the combustible gas mixture G immediately autoignites toproduce combustion products 132—namely, CO₂, CO, H₂O, and anyuncombusted fuel, oxygen, and/or other gas compounds such asnitrogen—that are discharged into and through the glass melt 98.Anywhere from five to thirty submerged burners 126 are typicallyinstalled in the SC melter 14 although more or less burners 126 may beemployed depending on the size and melt capacity of the melter 14.

During operation of the SC melter 14, each of the one or more submergedburners 126 individually discharges combustion products 132 directlyinto and through the glass melt 98. The glass melt 98 is a volume ofmolten glass that often weighs between 1 US ton (1 US ton=2,000 lbs) and20 US tons and is generally maintained at a constant volume duringsteady-state operation of the SC melter 14. As the combustion products132 are thrust into and through the glass melt 98, which create complexflow patterns and severe turbulence, the glass melt 98 is vigorouslyagitated and experiences rapid heat transfer and intense shearingforces. The combustion products 132 eventually escape the glass melt 98and are removed from the interior reaction chamber 104 through theexhaust vent 120 along with any other gaseous compounds that mayvolatize out of the glass melt 98. Additionally, in some circumstances,one or more non-submerged burners (not shown) may be mounted in the roof106 and/or the surrounding upstanding wall 110 at a location above theglass melt 98 to provide heat to the glass melt 98, either directly byflame impingement or indirectly through radiant heat transfer, and toalso facilitate foam suppression and/or destruction.

While the one or more submerged burners 126 are being fired into theglass melt 98, the vitrifiable feed material 96 is controllablyintroduced into the interior reaction chamber 104 through the feedmaterial inlet 116. Unlike a conventional glass-melting furnace, thevitrifiable feed material 96 does not form a batch blanket that rests ontop of the glass melt 98; rather, the vitrifiable feed material 96 israpidly disbanded and consumed by the agitated glass melt 98. Thedispersed vitrifiable feed material 96 is subjected to intense heattransfer and rapid particle dissolution throughout the glass melt 98 dueto the vigorous melt agitation and shearing forces induced by the directinjection of the combustion products 132 from the submerged burner(s)126. This causes the vitrifiable feed material 96 to quickly mix, react,and become chemically integrated into the glass melt 98. However, theagitation and stirring of the glass melt 98 by the direct discharge ofthe combustion products 132 also promotes bubble formation within theglass melt 98. Consequently, the glass melt 98 is foamy in nature andincludes a homogeneous distribution of entrained gas bubbles. Theentrained gas bubbles may account for 30 vol % to 60 vol % of the glassmelt 98, which renders the density of the glass melt 98 relatively low,typically ranging from 0.75 gm/cm³ to 1.5 gm/cm³, or more narrowly from0.99 gm/cm³ to 1.3 gm/cm³, for soda-lime-silica glass. The gas bubblesentrained within the glass melt 98 vary in size and may contain any ofseveral gases including CO₂, H₂O (vapor), Na, SO₂, CH₄, CO, and volatileorganic compounds (VOCs).

The vitrifiable feed material 96 introduced into the interior reactionchamber 104 has a composition that is formulated to provide the glassmelt 98, particularly at the molten glass outlet 118, with apredetermined glass chemical composition upon melting. For example, theglass chemical composition of the glass melt 98 may be asoda-lime-silica glass chemical composition, in which case thevitrifiable feed material 96 may be a physical mixture of virgin rawmaterials and optionally cullet (i.e., recycled glass) and/or otherglass precursors that provides a source of SiO₂, Na₂O, and CaO in thecorrect proportions along with any of the other materials listed belowin Table 2 including, most commonly, Al₂O₃. The exact materials thatconstitute the vitrifiable feed material 96 are subject to muchvariation while still being able to achieve the soda-lime-silica glasschemical composition as is generally well known in the glassmanufacturing industry.

TABLE 2 Glass Chemical Composition of Soda-Lime-Silica Glass ComponentWeight % Raw Material Sources SiO₂ 60-80 Quartz sand Na₂O  8-18 Soda ashCaO  5-15 Limestone Al₂O₃ 0-2 Nepheline Syenite, Feldspar MgO 0-5Magnesite K₂O 0-3 Potash Fe₂O₃ + FeO   0-0.08 Iron is a contaminant MnO₂ 0-0.3 Manganese Dioxide SO₃  0-0.5 Salt Cake, Slag Se    0-0.0005Selenium F  0-0.5 Flourines are a contaminant

For example, to achieve a soda-lime-silica glass chemical composition inthe glass melt 98, the vitrifiable feed material 96 may include primaryvirgin raw materials such as quartz sand (crystalline SiO₂), soda ash(Na₂CO₃), and limestone (CaCO₃) in the quantities needed to provide therequisite proportions of SiO₂, Na₂O, and CaO, respectively. Other virginraw materials may also be included in the vitrifiable feed material 96to contribute one or more of SiO₂, Na₂O, CaO and possibly other oxideand/or non-oxide materials in the glass melt 98 depending on the desiredchemistry of the soda-lime-silica glass chemical composition and thecolor of the glass articles being formed. These other virgin rawmaterials may include feldspar, dolomite, and calumite slag. Thevitrifiable feed material 96 may even include up to 80 wt % culletdepending on a variety of factors. Additionally, the vitrifiable feedmaterial 96 may include secondary or minor virgin raw materials thatprovide the soda-lime-silica glass chemical composition with colorants,decolorants, and/or redox agents that may be needed, as well as finingagents if such agents are desired to be introduced into the glass melt98 to complement the fining agents introduced into the molten glass bath22 by the dissolvable fining material component 68.

Referring now to FIGS. 1, 3, 5, and 11, the foamy molten glass 100discharged from the SC melter 14 through the molten glass outlet 118 isremoved from the glass melt 98 and is chemically homogenized to thedesired glass chemical composition, e.g., a soda-lime-silica glasschemical composition, but with the same relatively low density andentrained volume of gas bubbles as the glass melt 98. The foamy moltenglass 100 flows into the fining vessel 10 as the input molten glass 12either directly or through an intermediate stilling or holding tank thatmay settle and moderate the flow rate of the input molten glass 12. Theinput molten glass 12 is introduced into the fining chamber 20 throughthe inlet 24 and combines with and is subsumed by the molten glass bath22. The blending of the input molten glass 12 with the molten glass bath22 introduces the gas bubbles 88 into the glass bath 22. These gasbubbles 88 are removed from the molten glass bath 22 as the glass bath22 flows in the flow direction F from the inlet 24 of the fining vessel10 to the outlet 26.

As the molten glass bath 22 flows in the flow direction F, theundercurrent 62 of the glass bath 22 flows beneath the skimmer 50through the submerged passageway 60 to navigate molten glass past theskimmer 50. The undercurrent 62 is selectively and directly exposed tothe fining agent(s) that dissolve into the undercurrent 62 from thedissolvable fining material component 68, which, in this particularembodiment, is in the form of a solid plate 72 that is moveable alongthe height S_(H) of the skimmer 50. The fining agent(s) react with themolten glass to release fining gases into the undercurrent 62 and theportion of the molten glass bath downstream of the skimmer 50. Thesefining gases remove the gas bubbles 88 that pass through the submergedpassageway 60 by accelerating the ascension of the gas bubbles 88 orcausing the gas within the bubbles 88 to dissolve into the glass matrixof the molten glass bath 22. In that regard, the skimmer 50 may be usedto separate the entrained gas bubbles 88 introduced into the moltenglass bath 22 as discussed above to ensure that most of the gas bubbles88 that pass beneath the skimmer 50 are smaller gas bubbles having adiameter of 0.7 mm or less or, more preferably, 0.5 mm or less. As aresult, the density of the molten glass bath 22 increases along the flowdirection F of the glass bath 22, and the amount of the fining agent(s)introduced into the molten glass bath 22 may be limited to what isneeded to effectively remove the smaller gas bubbles that pass beneaththe skimmer 50.

The output molten glass 16 is removed from the outlet 26 of the finingvessel 10 and has a second density and a second concentration ofentrained gas bubbles. The second density of the output molten glass 16is greater than the first density of the input molten glass 12, and thesecond concentration of entrained gas bubbles of the output molten glass16 is less than the first concentration of entrained gas bubbles of theinput molten glass 12. For instance, the output molten glass 16 may havea density of 2.3 gm/cm³ to 2.5 gm/cm³ and a concentration of entrainedgas bubbles ranging from 0 vol % to 1 vol % or, more narrowly, from 0vol % to 0.05 vol %, for soda-lime-silica glass. The output molten glass16 may then be further processed into a glass article such as a glasscontainer. To that end, the output molten glass 16 delivered from theoutlet 26 of the fining vessel 10 may have a soda-lime-silica glasschemical composition as dictated by the formulation of the vitrifiablefeed material 96, and a preferred process 150 for forming glasscontainers from the output molten glass 16 includes a thermalconditioning step 152 and a glass article forming step 154, asillustrated in FIG. 12.

In the thermal conditioning step 152, the output molten glass 16delivered from the fining vessel 10 is thermally conditioned. Thisinvolves cooling the output molten glass 16 at a controlled rate toachieve a glass viscosity suitable for glass forming operations whilealso achieving a more uniform temperature profile within the outputmolten glass 16. The output molten glass 16 is preferably cooled to atemperature between 1000° C. to 1200° C. to provide conditioned moltenglass. The thermal conditioning of the output molten glass 16 may beperformed in a separate forehearth that receives the output molten glass16 from the outlet 26 of the fining vessel 10. A forehearth is anelongated structure that defines an extended channel along whichoverhead and/or sidewall mounted burners can consistently and smoothlyreduce the temperature of the flowing molten glass. In anotherembodiment, however, the thermal conditioning of the output molten glass16 may be performed within the fining vessel 10 at the same time themolten glass bath 22 is being fined. That is, the fining and thermalconditioning steps may be performed simultaneously such that the outputmolten glass 16 is already thermally conditioned upon exiting the finingvessel 10.

Glass containers are formed from the conditioned molten glass in theglass article forming step 154. In some standard container-formingprocesses, the conditioned molten glass is discharged from the spout 38at the end of the fining vessel 10 or a similar device at the end of aforehearth as molten glass streams or runners. The molten glass runnersare then sheared into individual gobs of a predetermined weight. Eachgob is delivered via a gob delivery system into a blank mold of a glasscontainer forming machine. In other glass container forming processes,however, molten glass is streamed directly from the outlet 26 of thefining vessel 10 or an outlet of the forehearth into the blank mold tofill the mold with glass. Once in the blank mold, and with itstemperature still between 1000° C. and 1200° C., the molten glass gob ispressed or blown into a parison or preform that includes a tubular wall.The parison is then transferred from the blank mold into a blow mold ofthe glass container forming machine for final shaping into a container.Once the parison is received in the blow mold, the blow mold is closedand the parison is rapidly outwardly blown into the final containershape that matches the contour of the mold cavity using a compressed gassuch as compressed air. Other approaches may of course be implemented toform the glass containers besides the press-and-blow and blow-and-blowforming techniques including, for instance, compression or other moldingtechniques.

The final container formed within the blow mold has an axially closedbase and a circumferential wall. The circumferential wall extends fromthe axially closed base to a mouth that defines an opening to acontainment space defined by the axially closed base and thecircumferential wall. The glass container is allowed to cool while incontact with the mold walls of the blow mold and is then removed fromthe blow mold and placed on a conveyor or other transport device. Theglass container is then reheated and cooled at a controlled rate in anannealing lehr to relax thermally-induced constraints and removeinternal stress points. The annealing of the glass container involvesheating the glass container to a temperature above the annealing pointof the soda-lime-silica glass chemical composition, which usually lieswithin the range of 510° C. to 550° C., followed by slowly cooling thecontainer at a rate of 1° C./min to 10° C./min to a temperature belowthe strain point of the soda-lime-silica glass chemical composition,which typically lies within the range of 470° C. to 500° C. The glasscontainer may be cooled rapidly after it has been cooled to atemperature below the strain point. Any of a variety of coatings may beapplied to the surface of the glass container either before (hot-endcoatings) or after (cold-end coatings) annealing for a variety ofreasons.

The glass melting, fining, and glass article forming processes describedabove are subject to variations without detracting from their purposesor objectives. Several such variations are depicted in FIGS. 7-9 inwhich like reference numerals are used to identify correspondingfeatures of the previously-described embodiments. In the discussionsbelow, only the material differences of the relevant embodiment arediscussed compared to the previously-described embodiments with theunderstanding that the descriptions of the various features of thepreviously-described embodiments are equally applicable unless statedotherwise. Referring now to FIG. 7, in one alternate embodiment, thedissolvable fining material component 268 supported within the skimmer250 may be a perforated plate 272, as opposed to a solid plate, in thatthe plate 272 defines a plurality of openings 275 that fully traversethe thickness of the plate 272. In this way, the undercurrent 62 of themolten glass bath 22 may flow both through and around the dissolvablefining material plate 272 to facilitate more intimate exposure betweenthe plate 272 and the undercurrent 62. Because the undercurrent 62 ofthe molten glass bath 22 flows both through and around the plate 272,the fining agent(s) may be released more uniformly into the undercurrent62.

In another alternate embodiment, as shown in FIG. 8, the dissolvablefining material component 368 may be in the form of a rod 372 as opposedto a plate 72, 272. Multiple dissolvable fining material rods 372 may beemployed together. To that end, the skimmer 350 includes a main body 376that defines a plurality of bores 378. Each bore 378 traverses theskimmer 350 along the height S_(H) of the skimmer 350 and is open at thedistal free end 358 and the opposed upper end 380 of the skimmer 350.Each of the bores 378 supports a dissolvable fining material rod 372.The rods 372 are movable relative to the main body 376 along the heightS_(H) of the skimmer 350 in the same way as the dissolvable finingmaterial plates 72, 272—that is, to maintain an exposed portion 374 ofthe rods 372 at the desired distance PD beyond the distal free end 358of the skimmer 350 as the rods disintegrate over time. And, much likethe perforated plate 272 of the embodiment illustrated in FIG. 7, theuse of multiple dissolvable material rods 372 allows the undercurrent 62of the molten glass bath 22 to flow through and around the rods 372,thus facilitating the release of the fining agent(s) from the rods 372more uniformly into the undercurrent 62.

In still another alternate embodiment, the dissolvable fining materialcomponent 468 may be supported within the housing 418 of the finingvessel 10, as depicted in FIGS. 9-10. In this scenario, a skimmer 481formed of a refractory material may extend downwardly from the roof 428of the housing 418 and between the sidewalls 432 c, 432 d of the housing418 to define, as before, the submerged passageway 460 along withcorresponding portions of the floor 430 and sidewalls 432 c, 432 d. Achannel 483 that extends across the fining chamber 420 and between thesidewalls 432 c, 432 d of the upstanding wall 432, and therefore runsalong the width S_(W) of the skimmer 481, is defined in the floor 430directly beneath the skimmer 481. A dissolvable fining material rod 472is received in the channel 483 and rises above the floor 430 a distanceW_(D) that is less than the distance T_(D) between a distal free end 485of the skimmer 481 and the floor 430 of the housing 418. And, similar tothe other embodiments, the fining material rod 472 is selectively anddirectly exposed to the undercurrent 62 of the molten glass bath 22 thatpasses through the submerged passageway 460 beneath the skimmer 481.Fining agent(s) are released into the undercurrent 62 to target the gasbubbles, which may comprise mostly smaller gas bubbles, in the same wayas before, albeit from the floor 430 of the housing 418. The finingmaterial rod 472 described here may also, if desired, be used inconjunction with the skimmers 50, 250, 350 disclosed in the previousembodiments as a way to increase the exposure of the undercurrent 62 tothe fining agent(s).

In yet another alternate embodiment, additional skimmers 589, which areshown in FIGS. 3-4, may be included in the fining vessel 10 downstreamof the skimmer 50, 250, 350 described above. Each of the additionaldownstream skimmers 589 may individually have the same structure as anyof the skimmers 50, 250, 350 described above that support a dissolvablefining material component 68, 268, 368 or it may have the same structureas the skimmer 481 that does not support a dissolvable fining materialcomponent. If additional skimmers 589 are included in the fining vessel10, in many instances the number of additional skimmers 589 may besomewhere between one and three.

There thus has been disclosed a method of fining glass that satisfiesone or more of the objects and aims previously set forth. After beingfined, the molten glass may be further processed into glass articlesincluding, for example, glass containers. The disclosure has beenpresented in conjunction with several illustrative embodiments, andadditional modifications and variations have been discussed. Othermodifications and variations readily will suggest themselves to personsof ordinary skill in the art in view of the foregoing discussion. Forexample, the subject matter of each of the embodiments is herebyincorporated by reference into each of the other embodiments, forexpedience. The disclosure is intended to embrace all such modificationsand variations as fall within the spirit and broad scope of the appendedclaims.

1. A method of fining glass, the method comprising: supplying inputmolten glass into a fining chamber of a fining vessel, the input moltenglass combining with a molten glass bath contained within the finingchamber and introducing entrained gas bubbles into the molten glassbath, the input molten glass having a density and a concentration of gasbubbles; flowing the molten glass bath through the fining chamber in aflow direction, the molten glass bath having an undercurrent that flowsbeneath a skimmer, which is partially submerged in the molten glassbath, and through a submerged passageway defined in part by the skimmer;and introducing one or more fining agents into the undercurrent of themolten glass bath directly beneath the skimmer from a dissolvable finingmaterial component.
 2. The method set forth in claim 1, whereinintroducing one or more fining agents into the undercurrent of themolten glass bath comprises releasing one or more fining agents from thedissolvable fining material component, the dissolvable fining materialcomponent being supported within the skimmer and having an exposedportion that protrudes beyond a distal free end of the skimmer into thesubmerged passageway.
 3. The method set forth in claim 2, wherein thedissolvable fining material component is in the form of a plate that ismoveable within an internal cavity defined in a main body of theskimmer.
 4. The method set forth in claim 3, wherein the plate isperforated to allow the undercurrent of the molten glass bath to flowthrough openings defined in the exposed portion of the plate.
 5. Themethod set forth in claim 2, wherein the dissolvable fining materialcomponent is in the form of a rod movable within a bore defined in amain body of the skimmer.
 6. The method set forth in claim 2, furthercomprising: advancing the dissolvable fining material component relativeto a main body of the skimmer along a height of the skimmer to maintainthe exposed portion of component as the component disintegrates in theundercurrent of the molten glass bath.
 7. The method set forth in claim1, wherein the fining vessel includes a housing that defines the finingchamber, the housing comprising a floor, and wherein introducing one ormore fining agents into the undercurrent of the molten glass bathcomprises releasing one or more fining agents from the dissolvablefining material component, the dissolvable fining material componentbeing supported in the floor of the housing directly beneath the skimmerand rising above the floor into the submerged passageway.
 8. The methodset forth in claim 7, wherein the floor defines a channel extendingacross the fining chamber beneath the skimmer, and wherein thedissolvable fining material component is in the form of a rod and isreceived within the channel defined in the floor of the housing.
 9. Themethod set forth in claim 1, wherein the one or more fining agents thatare introduced into the undercurrent of the molten glass bath include asulfate that decomposes to release O₂ and SO₂.
 10. The method set forthin claim 1, wherein the one or more fining agents that are introducedinto the undercurrent of the molten glass bath include sodium sulfate,Cr₂O₃, WO₃, carbon, aluminum, a carbonate, silicon carbide (SiC), anoxidized metal powder, or a combination thereof.
 11. The method setforth in claim 1, wherein the input molten glass has a soda-lime-silicaglass chemical composition.
 12. The method set forth in claim 1, furthercomprising: discharging output molten glass from the fining vessel, theoutput molten glass having a density that is greater than the density ofthe input molten glass and further having a concentration of gas bubblesthat is less than the concentration of gas bubbles of the input moltenglass.
 13. A method of producing and fining glass, the methodcomprising: discharging combustion products from one or more submergedburners directly into a glass melt contained within an interior reactionchamber of a submerged combustion melter, the combustion productsdischarged from the one or more submerged burners agitating the glassmelt; discharging foamy molten glass obtained from the glass melt out ofthe submerged combustion melter; supplying the foamy molten glass into afining chamber of a fining vessel as input molten glass, the inputmolten glass combining with a molten glass bath contained within thefining chamber and introducing entrained gas bubbles into the moltenglass bath, the input molten glass having a density and comprising up to60 vol % bubbles; flowing the molten glass bath through the finingchamber in a flow direction, the molten glass bath having anundercurrent that flows beneath a skimmer, which is partially submergedin the molten glass bath, and through a submerged passageway defined inpart by the skimmer; introducing one or more fining agents into theundercurrent of the molten glass bath directly beneath the skimmer froma dissolvable fining material component; and discharging output moltenglass from the fining vessel, the output molten glass having a densitythat is greater than the density of the input molten glass and furthercomprising less than 1 vol % bubbles.
 14. The method set forth in claim13, wherein introducing one or more fining agents into the undercurrentof the molten glass bath comprises releasing one or more fining agentsfrom the dissolvable fining material component, the dissolvable finingmaterial component being supported within the skimmer and having anexposed portion that protrudes beyond a distal free end of the skimmerinto the submerged passageway.
 15. The method set forth in claim 14,further comprising: advancing the dissolvable fining material componentrelative to a main body of the skimmer along a height of the skimmer tomaintain the exposed portion of component as the component disintegratesin the undercurrent of the molten glass bath.
 16. The method set forthin claim 13, wherein the fining vessel includes a housing that definesthe fining chamber, the housing comprising a floor, and whereinintroducing one or more fining agents into the undercurrent of themolten glass bath comprises releasing one or more fining agents from thedissolvable fining material component, the dissolvable fining materialcomponent being supported in the floor of the housing directly beneaththe skimmer and rising above the floor into the submerged passageway.17. The method set forth in claim 13, wherein the glass melt in thesubmerged combustion melter, as well as the molten glass bath in thefining vessel, have a soda-lime-silica glass chemical composition. 18.The method set forth in claim 17, further comprising: forming the outputmolten glass discharged from the fining vessel into at least one glasscontainer having an axially closed base and a circumferential wall, thecircumferential wall extending from the axially closed base to a mouththat defines an opening to a containment space defined by the axiallyclosed base and the circumferential wall.
 19. The method set forth inclaim 13, wherein the one or more fining agents that are introduced intothe undercurrent of the molten glass bath include sodium sulfate, Cr₂O₃,WO₃, carbon, aluminum, a carbonate, silicon carbide (SiC), an oxidizedmetal powder, or a combination thereof.
 20. A fining vessel for finingglass, the fining vessel comprising: a housing that defines a finingchamber, the housing having a roof, a floor, and an upstanding wall thatconnects the roof and the floor, the housing further defining an inletto the fining chamber and an outlet from the fining chamber; a skimmerextending downwards from the roof of the housing towards the floor ofthe housing and further extending across the fining chamber betweenopposed lateral sidewalls of the upstanding wall, the skimmer having adistal free end that together with corresponding portions of the floorand upstanding wall defines a submerged passageway; and a dissolvablefining material component disposed directly beneath the skimmer, thedissolvable fining material component comprising a mixture of a glasscompatible base material and one or more fining agents.